[GSOC] rtems GPIO API

[Andre Marques]

On 05/23/14 01:08, Alan Cudmore wrote:
> Hi Andre,
> Please see my comments below:
> Alan
>
> On 5/22/2014 6:30 PM, Andre Marques wrote:
>> Hello,
>>
>> I will start my GSOC project with a GPIO driver for the RPi BSP, and 
>> part of the GPIO driver code will not be specific to the RPi but to 
>> any board with a GPIO interface. With code reuse in mind and since I 
>> did not found any "generic" API for the GPIO interface in the RTEMS 
>> code base, I intend to propose here an initial *rough* draft of what 
>> this API may look like.
>>
>
> Do you think a gpio API has advantages over Pierre's driver/ioctl 
> based driver?
> https://github.com/pficheux/raspberry_pi/blob/master/RTEMS/gpio_driver
>

This API would not be the GPIO driver. It would be an interface with the 
GPIO hardware that would then be used by the driver to operate the GPIO 
peripheral. You may see this API as something similar to the GPIO macros 
in Pierre's driver.

> Feedback from others would be welcome. Pierre offered this as a 
> generic GPIO driver interface for RTEMS earlier, but did not get much 
> feedback.
>
>> To initialize the API:
>>
>> rtems_gpio_initialize (struct gpio_config)
>>
>> which would initialize the API with a specific GPIO peripheral 
>> configuration: number of gpio pins, gpio register addresses, ...
>>
>> To set a gpio pin as input or output (the direction would be a macro):
>>
>> rtems_gpio_direction (int gpio, int direction)
>
> Does the gpio serve as the GPIO pin number in this API?

Yes, gpio would be the pin number.
>
>>
>> To set a gpio pull resistor (either pull up/down or no pull resistor):
>>
>> rtems_gpio_set_Pull (int gpio, int pull)
>>
> Maybe use lower case 'p' for this api to be consistent.

Yes.

>
>> Some GPIO I/O:
>>
>> rtems_gpio_set(int gpio)
>> rtems_gpio_clr (int gpio)
>> rtems_gpio_read_value (int gpio)
>
> Use  rtems_gpio_get instead of read_value?

Yes, seems better (shorter).

>
>>
>> And interrupt management:
>>
>> rtems_int_enable (int gpio, rtems_interrupt_level int)
>> rtems_int_disable (int gpio)
>> rtems_int_clear (int gpio)
>
> Do you mean to have rtems_gpio_int_xxx  ?

Yes, I forgot the gpio part when writting.

>
>>
>> Would appreciate some feedback on this.
>>
>> --Andre Marques.
>> _______________________________________________
>> rtems-devel mailing list
>> rtems-devel at rtems.org
>> http://www.rtems.org/mailman/listinfo/rtems-devel
>